A Branch-and-Price Algorithm for the Double Vehicle Routing Problem with Multiple Stacks and Heterogeneous Demand

This paper introduces the Double Vehicle Routing Problem with Multiple Stacks and Heterogeneous Demand (DVRPMSHD). This problem is a more realistic generalization of the Double Vehicle Routing Problem with Multiple Stacks when customers have heterogeneous demands and the demand of each customer cannot be divided among two or more vehicles. The objective of this problem is to find optimal routes for a fleet of vehicles to visit all pickup and delivery locations while ensuring the feasibility of the loading plan. An integer linear programming and a branch-and-price algorithm are proposed. The computational results show that our branch-and-price algorithm is able to find the optimal solution for most of the instances reported and find better solutions than those found by the integer linear programming formulation for some instances.